High-mobility perovskite BaSnO3 films are of significant interest as new wide bandgap semiconductors for power electronics, transparent conductors, and as high mobility channels for epitaxial integration with functional perovskites. Despite promising results for single crystals, high-mobility BaSnO3 films have been challenging to grow. Here, we demonstrate a modified oxide molecular beam epitaxy (MBE) approach, which supplies pre-oxidized SnOx. This technique addresses issues in the MBE of ternary stannates related to volatile SnO formation and enables growth of epitaxial, stoichiometric BaSnO3. We demonstrate room temperature electron mobilities of 150 cm2 V−1 s−1 in films grown on PrScO3. The results open up a wide range of opportunities for future electronic devices.

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Long-term stability of high- and low-resistance states in full-organic ferroelectrically gated graphene transistors is an essential prerequisite for memory applications. Here, we demonstrate high retention performance for both memory states with fully saturated time-dependence of the graphene channel resistance. This behavior is in contrast with ferroelectric-polymer-gated silicon field-effect-transistors, where the gap between the two memory states continuously decreases with time. Before reaching saturation, the current decays exponentially as predicted by the retention model based on the charge injection into the interface-adjacent layer. The drain current saturation attests to a high quality of the graphene/ferroelectric interface with low density of charge traps.

The electrical and structural characteristics of SmTiO 3 /SrTiO 3 /SmTiO 3 and GdTiO 3 /SrTiO 3 /GdTiO 3 heterostructures are compared. Both types of structures contain narrow SrTiO 3 quantum wells, which accommodate a confined, high-density electron gas. As shown previously [Phys. Rev. B 86, 201102(R) (2012)] SrTiO 3 quantum wells embedded in GdTiO 3 show a metal-to-insulator transition when their thickness is reduced so that they contain only two SrO layers. In contrast, quantum wells embedded in SmTiO 3 remain metallic down to a single SrO layer thickness. Symmetry-lowering structural distortions, measured by quantifying the Sr-column displacements, are present in the insulating quantum wells, but are either absent or very weak in all metallic quantum wells, independent of whether they are embedded in SmTiO 3 or in GdTiO 3 . We discuss the role of orthorhombic distortions, orbital ordering, and strong electron correlations in the transition to the insulating state.3

We examine the carrier density dependence of the scattering rate in two- and three-dimensional electron liquids in SrTiO3 in the regime where it scales with Tn (T is the temperature and n ≤ 2) in the cases when it is varied by electrostatic control and chemical doping, respectively. It is shown that the scattering rate is independent of the carrier density. This is contrary to the expectations from Landau Fermi liquid theory, where the scattering rate scales inversely with the Fermi energy (EF). We discuss that the behavior is very similar to systems traditionally identified as non-Fermi liquids (n < 2). This includes the cuprates and other transition metal oxide perovskites, where strikingly similar density-independent scattering rates have been observed. The results indicate that the applicability of Fermi liquid theory should be questioned for a much broader range of correlated materials and point to the need for a unified theory.